Single-tube forced-circulation heat transfer devices



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SINGLE-TUBE FORCED-CIRCULATION HEAT TRANSFER DEVICES FiledNov. 8. 1966Sheet 8 of 8 Luamu Fame-me new; roman. 131m United States Patent3,431,893 SINGLE-TUBE FORCED-CIRCULATION HEAT TRANSFER DEVICES LucienFrdric Henri Marcel Fouch, Neuilly-sur-Seme, and Marc Roger Armand,Saint-Germain-en-Laye, France,, assignors to Fives-Penhoet, Paris,France, a French body corporate Filed Nov. 8, 1966, Ser. No. 592,852Claims priority, application6France, Nov. 8, 1965,

Us. Cl. 122-32 11 Claims Int. Cl. F22b 1/08 ABSTRACT OF THE DISCLOSUREIt is the essential object of the present invention to provide asingle-tube forced-circulation heat-transfer device, preferably of thesteam-generator type, comprising clusters of straight verticallydisposed tubular elements through which a fluid to be vaporized iscirculated, said tubular elements being housed in at least one casing inwhich a heat-bearing fluid circulates in countercurrent relationship tothe fluid to be vaporized.

A heat transfer device of this character is intended more particularlyfor use in a nuclear plant wherein the heat transfer device lies withinan enclosure containing the nuclear reactor. In a plant of this type theheat bearing fluid to be cooled consists as a rule of carbon dioxideconstituting the reactor coolant, the fluid to be heated consisting ofwater.

It is known that the water circulating in the heat transfer is insuccession, as it flows through said straight tubular elements, in theliquid state in a first, so-called economizer section, in the state of awater and vapour mixture in a second, so-called vaporizer section, andfinally in the vapour state in a third, so-called superheater section.

The fact that these heat transfer devices must be housed within anenclosure containing a reactor is attended by serious inconveniences,due to the reduced space available, notably in connection with thefitting of the various water-supply and steam delivery pipelines whichdo not partake directly in the heat transfer cycle, since the greatestpossible number of tubular heat transfer elements must be accommodatedin order to obtain the maximum efficiency. Similar difliculties areexperienced in connection with the accommodation of the supportingstructure.

On the other hand, these heat transfer systems were hardly accessibleduring the reactor operation, thus precluding any repair works duringthe actual service time, and therefore asymmetric conditions must beavoided in the cooling of the heat-bearing fluid in case some of thetubular elements were not supplied with water.

It is the primary object of the present invention to provide a heattransfer device particularly adapted to the various requirements to bemet in the equipment of nuclear plants, and remarkable notably in thatit consists of identical superposed unitary panels comprising a numberof identical tubular elements, said panels being grouped into separateidentical units constituting each an elementary heat transfer unit, saidunits being so assembled as to have the shape of a polygonal annulus ina plane at right 3,431,893 Patented Mar. 11, 1969 angles to the axes ofsaid tubular elements, and to leave on the one hand between the outercontour of said annulus and the wall of the enclosure in which saidunits are housed, and on the other hand in the central portion of saidannulus, free spaces adapted to receive the supporting structure andpermit the passage of the watersupply and steam-outlet pipes.

This arrangement also permits more particularly of obtaining a perfectlyhomogeneous distribution of a very considerable number of heat-transfertubular elements in the enclosure containing the reactor whilepreserving the passages necessary for the access to the upper portion ofthe heat transfer system. Thus, a high filling coefficient is obtained,with a corresponding increment in the heat transfer efliciency and arational utilization of the space available in the enclosure.

A ccording to another feature of this invention the aforesaid units areassembled with a view to have the general configuration of a hexagonalannulus.

This hexagonal shape is particularly advantageous if the enclosure has acircular contour.

According to a further feature of this invention each unitary panelaforesaid consists of a sheet of tubular elements each having its axisdisposed in a common plane and connected at either ends to a singleheader having its axis coplanar with the axes of said tubular elements.

With this distribution of the tubular elements into flat panels adaptedtherefor to be easily juxtaposed the manufacture and mounting of theheat transfer device are considerably simplified.

According to another feature characterizing this invention, the tubularelements of each panel are connected to at least one of said headers bymeans of flexible connecting tubings having their axes coplanar with theaxes of said tubular elements, the pitch of the connections between saidtubings and the relevant header being smaller than the pitch of thetubular elements.

The fact of providing flexible tubings permits of compensatingdifferential expansions likely to take place between the various tubesof a same panel and the fact that these flexible tubings (which partakeonly accessorily in the heat transfer process) may consist of simplepipe sections having a diameter smaller than that of said tubularelements, permits of disposing the connecting points at a shorterrelative spacing than that permitted by a direct connection of thetubular elements. Under these conditions, headers having a lengthinferior to the panel length may be used, and thus space is saved whichmay advantageously be used for the passage of the various inlet andoutlet pipes.

According to another advantageous feature of this invention, theaforesaid units are of polygonal configuration When seen in a sectiontaken at right angles to the axes of the tubular elements.

These units may have a rectangular, square, lozenge, parallelogram,hexagonal or regular or nonregular polygonal cross-sectionalconfiguration, or these cross-sectional shapes may be selected as afunction of the room available for the heat transfer device in theenclosure containing the nuclear reactor.

According to a specific form of embodiment of the invention, theaforesaid units are of lozenge configuratron in cross-section.

This lozenge-shaped cross-sectional contour permits of obtaining anequilateral triangular pitch for the tubular cluster, which isadvantageous in that it affords a better uniformity in the distributionof the heat-bearing gas; moreover, in case the enclosure in which theheat transfer device has a circular configuration, the use oflozengeshaped units affords an optimum utilization of the spaceavailable therein.

Still according to this invention, a plurality of separate circuits forthe fluid to be heated, for example four circuits, are provided, everyfourth panel of a same unit being connected to each circuit aforesaid.

Thus, four completely separate but mutually imbricated heat transferdevices are actually obtained, whereby in case of faulty supply of oneor a plurality of these heat transfer devices any extremely detrimentalasymmetry in the cooling of the reactor coolant is definitely avoided.

Other features and advantages of this invention will become apparent asthe following description proceeds with reference to the accompanyingdrawings illustrating diagrammatically by way of example various formsof embodiment of the invention which should not be construed as limitingthe scope of the invention. In the drawings:

FIGURE 1 illustrates in diagrammatic form a heat transfer deviceconstructed according to the teachings of this invention, as seen fromabove, with a partial section taken upon the four sectors A, B, C, and Din order to show various component elements of the heat transfer devicewhich lie at different levels;

FIGURE 2 is an elevational view With parts broken away to illustrate oneportion of the heat transfer device which comprises a unitary panel;

FIGURE 3 is a detail section taken on a larger scale along the lineIIIIII of FIGURE 2;

FIGURE 4 is a fragmentary elevational view of the heat transfer deviceshowing two units consisting of juxtaposed unitary panels, one of theseunits being shown in external view and the other in section;

FIGURE 5 is a fragmentary view showing on a larger scale the upperportion of a unit of the type shown in FIGURE 4;

FIGURE 6 is an elevational view showing the superposed sheets of tubesfeeding the water headers of a unitary panel;

FIGURE 7 is a section taken upon the line VII-VII of FIGURE 6;

FIGURE 8 is a section taken upon the line VIII-VIII of FIGURE 6;

FIGURE 9 is a plane view from above of a unit showing in diagrammaticform the steam headers and the steam outlet tubes connected to theseheaders;

FIGURE 10 is a perspective view showing on a larger scale the mountingof the steam headers on the flanges of the supporting structure;

FIGURE 11 is a plane view from above of the supporting structure of theheat transfer device, and

FIGURE 12 is a section taken upon the line XII-XII of FIGURE 11.

The attached drawings illustrate a typical form of embodiment of thepresent invention which consists of a single-tube heat-transferforced-circulation steam generator housed in an enclosure containing anuclear reactor and intended for cooling the gaseous cooling fluid ofthis reactor, the circulation of this cooling fluid taking place in thedownward direction and the fluid to be heated, water and water vapour,is circulated in the opposite or upward direction.

This heat transfer device is illustrated diagrammatically in FIGURE 1 inorder clearly to show the relative arrangement of its various componentelements.

To this end, FIGURE 1 is divided into four sectors A, B, C and Dcorresponding to three sections taken in three different planes (A, B,C), and to a plane view from above (D). Sector A corresponds to thelower portion of the heat transfer device. Sector B shows the sheets oftubes supplying water to the water headers. Sector C shows the waterheaders located at the lower portion of the unitary panels. Finally,sector D shows the steam outlets tubes.

This heat transfer device consists essentially of plane unitary panels 1(see FIGURE 2) comprising each a number of vertical straight tubularelements 2 constituting a sheet of tubes having coplanar axes, and twoheaders 3, and 4, header 3 being at the lower portion of the panel forsupplying liquid water thereto, the other header 4 being disposed at theupper portion of the panel to receive the outgoing steam; the axes ofthese headers are coplanar with those of the tubular elements. Thesepanels 1 are juxtaposed to constitute separate, lozenge-shaped unitsdesignated by the reference numeral 5. Each unit constituting a completeelementary heat transfer device, is fed with liquid water from a clusterof bent tubes designated as a whole by the reference numeral 6 anddisposed beneath the water header 3. Each unit further comprises abovethe steam headers 4, clusters of water steam outlet tubes designated asa whole by the reference numeral 7.

FIGURE 1 also shows the water-feed and steam outlet bulbs 8 which are nopart of the present invention, together with the water supply pipes 9(connected to the clusters 6) and the steam delivery pipes 10 (connectedto tubes 7).

The lozenge-shaped units 5 are assembled with a view to constitute ahexagonal annulus 11 leaving on the one hand a central free space 12 andon the other hand, several free spaces 14 between the external sides ofthe hexagonal annulus 11 and the wall 13 of the circular enclosure.Through these spaces 12 and 14 access may be had to the upper portion ofthe heat transfer device; they permit the passage of the downwardlyextending steam outlet pipes 10 connected to the steam outlet tubes 7,and also of the various pipe lines connected to the reactor: sheathfailure detector, CO filtration means, etc. These spaces are also usedfor disposing the structure elements supporting the units 5, notably theposts carrying the upper framework 15 such as the column 16 disposedcentrally of the enclosure.

The number of tubes constituting each unitary panel 1 is relatively highand selected as a function of the network pitch limiting the diameter ofthe headers, the perrnissible length of these headers, the maximumpermissible dimensions of each panel, these dimensions being subordinateprimarily by the space available in the enclosure in which the heattransfer device is to be housed, and also by the inherent handling andtransport problems. In the case illustrated the panel 1 comprisesthirty-two tubular elements 2.

The tubular elements 2 are connected to the water header 3 by means offlexible tubings 17 capable of absorbing differential thermal expansionslikely to take place between the various tubular elements of a samepanel. These tubings 17 are so disposed that their axes are coplanarwith those of the tubular elements 2 and also with those of the headers3 and 4 (see FIGURE 3).

Each tubing 17 comprises two successive and oppositely directed bends18a, 18b and consists therefore of three substantially rectilinearsections 19a, 19b, 19c. These tubings 17 are disposed symmetrically withrespect to a plane P normal to the panel which is disposed centrally ofthe headers 3 and 4. In the left-hand half of the panel (as seen inFIGURE 2) the end tubing has its first section 19a inclined from rightto left, its second section 1% inclined from left to right, and finallyits third section inclined again from right to left. Of course, thesections 19a, 18b and 19c of the end tubing of the right-hand half panelare inclined in opposite directions.

The tubings 17 in which water in the liquid state circulates require asmaller cross-sectional passage area than the tubular elements 2.Advantage will be taken of this narrower cross-sectional dimension forconsiderably reducing the relative pitch of the connections betweenthese tubings 17 and the water header 3 with respect to the pitch of thetubular elements themselves. Thus, the header 3 may be given a lengthconsiderably smaller than the relative spacing of the two endmosttubular elements of the panel. This pitch difference is compensated bygradually modifying the inclination of the third section 190 of eachconnecting tubing 17. Whilst the angular value of the bend between thefirst section 19a and the secend section 19b remains unchanged in allthe tubings 17, whether in the first or left-hand half-panel or in thesecond or right-hand half-panel, the angle between the second section19b and the third section 190 increases gradually from the tubingremotest from the aforesaid plane of symmetry P to the tubing nearestthereto, this third section in the specific case of the two centraltubings, being substantially coextensive with the tubular element towhich they are connected.

This symmetrical arrangement of tubings 17 with respect to said plane ofsymmetry P permits of disposing these tubings within the space boundedby the two endmost tubular elements of the panel.

The tubular elements 2 may consist of ribbed or finned tubes, or plaintubes, and if desired internal means may be provided therein forincreasing the coefiicient of heat transfer. These tubular elements havewaisted end portions (see FIGURES 3 to 5) to eliminate welding steps.These waisted portions 20' are as long as possible so that each tubularelement can be connected directly to the relevant header. These waistedportions are obtained for example by removing the external fins of thetubular element at the ends thereof.

All the unitary panels 1 thus obtained are identical in that theycomprise the same number of tubular elements having the same length;only the upper waisted portions of these tubular elements have differentlengths, in the case of juxtaposed panels, so that by properlyoffsetting the steam headers 4 to each other in the vertical directionthe best use can be made of the space available at the upper portion ofeach unit the space left free between the waisted portions of two oddorder tubular elements being adapted for example, to receive the headersof evenorder panels. As a result, the steam headers 4 constitute tworows disposed at different levels, the headers of one row correspondingto the gaps formed between the headers of the other row (see FIGURES 3to 5).

The aforesaid unitary panels are so juxtaposed as to constitute unitshaving, in the case illustrated, a lozenge configuration which, in thecase of a circular enclosure, afiords, the best possible filling andwhich, while permitting on the other hand the distribution of thetubular elements according to an equilateral triangular pitcharrangement, ensures an optimum distribution of the heatbearing gas.

It should be noted that to avoid the transport of unduly heavy andcumbersome units, these lozenge-shaped units may be divided in turn intoa plurality of parallelograms corresponding each to a subunit.

Each unit 5 constitutes a partial elementary heat transfer devicecomprising its inherent water supply pipes and steam outlet pipes, aswell as its casing 22 constitut ing a passage for the downwardly flowingheat-bearing gas.

The pipes supplying water to the lower headers 3 of each unit are bentto a hairpin configuration (see FIGURES 6 and 7) to constitute fiatsheets 6a, 6b, 6c, 611 to which an external contour corresponding tothat of the unit with which said supply pipes are associated, that is, alozenge configuration in the specific case contemplated herein. Thesesheets of supply pipes extend at right angles to the circulation of theheat-bearing gas, and furthermore they are superposed to one another.Thus, a cluster of tubes 6 is obtained which takes an active part in theheat transfer process and due to its position at the end of the gaspath, therefore where the highest temperature diiferences are obtained,it enables this cluster to homogenize these temperatures.

These superposed sheets 6a, 6b, 6c, 6d are advantgeo-usly so orientedthat the rectilinear sections of the tubes extend parallel to thevarious sides of the quadrilateral bounding the heat transfer unit;thus, in the case illustrated, the various sheets are alternatelyparallel to the sides of the lozenge. Thus, a squ ared clusterparticularly efiicient for gas mixing purposes is obtained.

Moreover, the fact of bending these water supply pipes imparts asufiicient flexibility thereto to take up lpossible expansions anddistortions.

It is known that, as a rule, it is advantageous to provide in a heattransfer system not a single water circuit but a plurality of completelyindependent water circuits. Each unit of the heat transfer deviceaccording to this invention is connected to four separate feed circuitsto which the unitary panels are connected. In order to ensure themaximum possible homogeneity, these heat transfer units are i'mbricatedinto each other by disposing the panels in such a manner that any pairof adjacent panels are connected to two separate circuits. In the caseillustrated, each circuit supplies every other four panels in each unit.FIGURE 8 shows the manner in which the headers 3 and the sheet of tubes6 are interconnected. As these headers are juxtaposed in the order 3a3b, 3c, 311, 3a, 3b, etc., all the headers bearing the same index areconnected to one of the sheets bearing the same index.

With this arrangement the gaseous streams are homogeneously cooled evenin case a plurality of panels connected to a same circuit were not fedwith water whilst the adjacent panels are still supplied with water.

The steam outlet tubes 7 connected to headers 4 are so disposed as toconstitute flat sheets arranged preferably horizontally. Each tube 7corresponds to one of the separate circuits and is connected to everyfour steam headers by means of connecting pipes 21 opposite to thetubular elements 2, that is emerging from the upper portion of theheaders 4 (see FIGURES 4 and 5).

FIGURE 9 shows the manner in which the headers 4 are connected to thesheets of tubes 7. All the headers 4a (corresponding to the waterheaders 3a) are connected to a same steam tube 7a by means of pipe lines21a. Similarly, the headers 4b, 4c, 4d are connected to the tubes 7b,7c, 7d by means of pipe lines 21b, 21c and 21d, respectively.

The casings 22 surrounding each unit extend from the steam headers 4 tothe clusters of water feed pipes. The function of these casings is toguide the flow of heat bearing gas about the tubular elements 1. Thiscasing is adapted to receive a detachable cover or like end member ateach upper and lower end so as to constitute a fluidtight enclosureadapted to be filled with an inert gas or connected to anair-conditioning circuit in order to protect the tubes against thedetrimental action of moisture and dust during transport and storageperiods, until the plan is actually put into service.

The structure supporting the units 5 comprises an upper horizontalframework 15 consisting of crossed beams or girders 25 forming lozengescorresponding to the sectional configuration of the units, plates 24being mounted on these beams of girders. This framework is supported inturn by the central post 16 received in the recess 12 (FIGURE 1), and onbrackets or like members 28 secured to the skirt 29 supporting thereactor proper. Each unit is supported at its upper portion by plates 24on which it bears through the medium of elements supporting the unitarypanels. In the case illustnated, each panel 1 is supported by the steamheaders 4. The plates 24 have notches 26 formed therein, these notches26 being adapted to be firmly engaged by the correspondingly shaped endpieces 27 secured to the ends of headers 4 (see FIGURE 10). The notches26 are so spaced as to ensure the distribution of headers 4 in twosuperposed rows as mentioned hereinabove; the difference in depthbetween any pair of successive notches corresponds to the diiference inlevel between these two rows, The plates supporting the unitary panelsof a same unit constitute the upper portion of the casing of this unit.

Although the heat transfer device illustrated is designed for an upwardwater circulation, it is obvious that this device could be disposedupside down, if desired, so that a downward water circulation beobtained, the heat hearing gas circulating in the upward direction.

Many modifications may be brought to the form of embodiment illustratedwithout inasmuch departing from the scope of the invention. Thus, forexample, the flexible connecting tubings 17 may be mounted on the steamoutlet side, that is, between the headers 4 and tubes 7. Similarly thecentral post 16 may be replaced by several posts, for example six postsdisposed at six corners of the inner hexagonal space 12, and thebrackets 28 may be replaced by posts disposed at the periphery of thehexagonal annulus 11.

Of course, the invention is not limited by the form of embodimentdescribed and illustrated which is given by way of example only.

What we claim is:

1. A single-tube forced-circulation heat transfer device constitutingpreferably a steam generator comprising a substantially cylindricalvertical enclosure Within which a heat-bearing fluid is circulated inaxial direction, identical juxtaposed plane unitary panels locatedwithin said enclosure and within which a fluid under pressure to beheated is circulated, each one of said panels comprising a number ofidentical straight vertically disposed tubular elements constituting asheet of tubes having coplanar axes an upper header and a lower headerthe axes of said headers being coplanar with those of said tubularelements, each one of said tubular element having its upper endconnected to said upper header and its lower end connected to said lowerheader, said panels being grouped into separate identical unitsconstituting each an elementary heat transfer device, a separate casingmember for each one of said units, a supporting structure for said unitsand said casing members, water supply and steam outlet pipes forsupplying water to said units and evacuating steam therefrom, said unitsbeing so assembled as to have in a plane at right angles to the axis ofsaid tubular elements the form of a polygonal annulus having an outercontour and a central portion and to leave on the one hand between saidouter contour and said enclosure and on the other hand in said portion,free spaces for receiving said supporting structure as well as saidwater-supply and steam-outlet pipes.

2. Device according to claim 1, wherein said annulus is a hexagonalannulus.

3. Device according to clairn 1, wherein said tubular elements of eachpanel have a constant pitch and wherein flexible connecting tubingshaving their axes coplanar to those of the tubular elements are providedfor connecting each one of said tubular elements to one at least of saidheaders, said connecting tubings comprising two successively oppositelydirected bends and being disposed symmetrically in relation to a planeof symmetry norm-a1 to the plane of the coplanar axes of said tubularelements and passing through the center of said headers, the connectionsbetween said connecting tubings and the corresponding header having aconstant pitch, said pitch being inferior to the pitch of the tubularelements.

4. Device according to claim 3, wherein each one of said connectingtubings comprises, in the direction of circulation of said fluid to beheated, first, second and third substantially rectilinear sections, theangle formed between said first and second sections being substantiallythe same in all the tubings of a same half panel, the angle between thesecond and third sections increasing in each half panel from the tubingremotest from the plane of symmetry to the tubing nearest to said planeof symmetry.

5. Device according to claim 4, wherein the third section aforesaid ofeach one of the two connecting tubings connected to the two centraltubular elements are substantially in axial alignment with said tubularelements.

6. Device according to claim 1, wherein said units have a lozengeconfiguration in section.

7. Device according to claim 6, wherein said lozengeshaped units consistof subunits having the shape of parallelograms inscribed in eachlozenge.

8. Device according to claim 1, wherein said supporting structurecomprises an upper horizontal framework consisting of crossed beams onwhich plates or like members are mounted which constitute the upperportions of said casings and supporting said unitary panels.

9. Device according to claim 8, wherein said plates are provided withnotches or the like engageable by said upper headers.

10. Device according to claim 8, wherein said crossed beams aresupported by brackets or posts, disposed at the periphery of saidannulus.

11. Device according to claim 8, wherein said supporting structurecomprises a single supporting post coaxial to said annulus.

References Cited UNITED STATES PATENTS 3,018,764 1/1962 Huet 122-343,104,652 9/1963 Tillequin et al. 122-32 3,117,559 1/1964 Fouehe 122-323,294,070 12/1966 Bell 12232 3,254,634 6/1966 Vorkauf 122235 KENNETH W.SPRAGUE, Primary Examiner.

US. Cl. X.R. 1225l0

